Biocidal products are used in numerous areas, such as for controlling growth of bacteria, fungi, and algae, for example. Without biocides, microbes can develop spores and grow on the surface of polymeric materials or spoil industrial products, resulting in allergic reactions, unpleasant odors, staining, discoloration, and loss of physical properties to name a few. The latter is known to lead to premature product failure.
Use of biocides in polyvinyl chloride (PVC) and other synthetic polymers is commonly directed to either protection of the susceptible polymer material from attack by microorganisms and/or achievement of biocidal surfaces. Polymer so protected, i.e., by incorporation of biocides, is known in the art as preserved polymer.
It is well-established that certain plastic materials like flexible PVC, polyurethanes or silicone may be easily attacked by microorganisms leading to discoloration or mechanical failure (R. Borgmann-Strahsen, Microbiocides for PVC and Other Polymers, in Industrial Biocides—Selection and Application, Royal Society of Chemistry, 2002, pg. 103-107, ed. D. R. Karsa and D. Ashworth). The susceptibility to microbial attack is mainly attributed to the plasticizer content of the plastic materials, as well as other additives such as stabilizers and antioxidants. The predominant organisms on the surface of those plastics are fungi and actinomycetes.
Due to the propensity of microorganisms to attack and/or consume plasticizers, the primary use of most organic biocides as additives for plastics is as fungicides (fungistats) in flexible or semi-flexible PVC. Such consumption of PVC plasticizers may lead to mechanical failure due to embrittlement, discoloration and malodor.
In terms of their susceptibility to microbial attack, these plasticizers can be grouped as follows: highly susceptible types, moderately susceptible types and low susceptible types. Highly susceptible plasticizers include sebacates, epoxidized oils, polyesters, and glycolates (see also a Ochs, Antimicrobials, in: Plastics Additives Handbook, 5th edition, pg. 647-680; editor: Hans Zweifel; Hanser Publishers, Munich, 2001). Among the moderately susceptible plasticizers are adipates and azelates while the group of low susceptible plasticizers is comprised of phthalates, phosphates, and chlorinated hydrocarbons.
Selected biocides, e.g. fungicides, that are used to protect plastic materials against attack from microorganisms include 10,10′-oxybisphenoxarsine (OPBA), 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), 2-n-octyl-4-isothiazolin-3-one (OIT), n-butyl-1,2-benzisothiazolin-3-one (BBIT), 2,4,4′-trichloro-2′-hydroxy-diphenyl-ether (TCPP), 3-iodo-2-propynyl butyl carbamate (IPBC), N-(tricholomethylthio phthalamide), zinc pyrithione (ZNP), 2-(4-thiazolyl)-benzimidazol (TBZ), carbendazim and 3-benzo[b]thien-2-yl-5,6-dihydro-1,4,2-oxathiazine 4-oxide (cf. Townsend Solutions, Townsend's Eighth Report on the Global Plastics Additives Market, Houston, Tex., 2012).
Several commercially available organic biocides are formulated and supplied in a plasticizer carrier. For example, OIT is supplied at varying concentrations in dioctylphthalate, diisononylphthalate, epoxidized soybean oil, and diisodecylphthalate (a more complete listing is provided at D. Ochs, Antimicrobials, in: Plastics Additives Handbook, 5th edition, pg. 647-680; editor: Hans Zweifel; Hanser Publishers, Munich, 2001).
Several patents and patent applications relate to organic biocides and plasticizers, as referred to hereinbelow.
U.S. Pat. No. 4,728,540 describes a process for introducing into already manufactured and fabricated vinyl products special function additives which impart to the vinyl product some useful property which it did not possess before as, for example, UV resistance, mildew resistance, etc. The process involves the use of vinyl plasticizers in which the additives are readily soluble to convey the additives into already manufactured and fabricated vinyl plastic products. Special function additives include UV stabilizers, mildewcides, fragrances, fungicides, antifogging agents, biocides, disinfectants, lubricants, antioxidants, water repellents, thickeners, surfactants, bacteriacides, vinyl heat stabilizers, antistats, release agents, anti blocking agents and the like.
U.S. Pat. No. 5,236,972 describes a thermoplastic powder slurry for making fiber reinforced composite structure prepregs having tack, drape and easy handleability. A slurry of thermoplastic resin powder suspended in a solution of distilled water, a water-soluble polymer, a wetting agent, a biocide, a plasticizer and an antifoamer, which is used to impregnate suitable reinforcing fibers, either continuous or woven, makes a prepreg having tack, drape and easy handleability.
U.S. Pat. No. 5,358,979 discloses a microbiocide-containing concentrate for use in thermoplastic polymers as well as in plastisols. The concentrate is primarily solid at ambient conditions and comprises from 1-30 wt % of a microbiocide, a polymer plasticizer and up to 20 wt % of a thermoplastic resin. These concentrates are primarily useful as masterbatch compositions used for incorporation into polymers in order to protect said polymers from fungal or bacterial attack. Also disclosed are processes for incorporating these materials into a polymer or plastisol, and polymers or plastisols made by these processes.
U.S. Pat. No. 5,585,407 relates to water-based coatable compositions for application to a substrate to inhibit the growth of microbes for extended periods of time, durable removable biocidal polymeric coatings resulting from such coatable compositions, a method of protecting a substrate from the growth of microbes and substrates resistant to such growth. The coatable compositions comprise an acrylate emulsion polymer comprising the reaction product of one or more acrylate or methacrylate monomers and one or more carboxylic acid monomers, an organoalkoxysilane, an effective amount of biocide, plasticizer and water.
Japanese Patent No. 11349415 (Abstract) discloses industrial biocide compositions containing epoxidized soybean oil as a diluent.
Notwithstanding the above literature, there is a continuing need for improved biocides such as bio-based biocides derived from natural resources.